Hi all I've had the bike out a couple of times now and as its a special (bitsa ) was just wondering what sort of engine revs I should be getting at certain road speeds and best way to measure them? I only ask as some of you are aware it has a norton box so I'm wondering if it might be a bit low geared as it seems to pull up quite easily from quite low road speeds in 4th.
Hi Neil, generally Burman and AMC gearboxes are a 1:1 ratio in top gear so "if" it is under geared its more likely to be the primary and drive sprocket combinations, if you have a copy of the Bacon restoration book the sprocket details and gearbox ratios are in the back.
Mine will do 72.1mph and it's in standard out of the Dutch Army trim. Now I did make use of a nice hill to get that speed but it does half shift for a little 350. Not sure of RPM, at that speed you start to think about how much effort it will be to slow it back down.
Tazmantic wrote: ↑Tue Apr 12, 2022 11:45 pm
Cheers Duncan, it might be as it should be as I’ve never ridden a standard one so can’t compare and no I don’t have that book are they available ?
My '54 G3/LS is also fitted with an AMC gearbox and clutch assembly. Be aware that the AMC clutch (if you're using it) has 42 teeth instead of the 40 teeth on the Burman clutch. I kept the 18 tooth engine sprocket as that was in good condition and relatively expensive to replace. That meant that the overall top gear ration changed from 5.83:1 to 6.12:1 which was a 5% lowering of the overall ratio, which I considered unacceptable. I opted to replace the standard 16 tooth gearbox sprocket to bring the gearing back up again. A 17 tooth sprocket would bring the overall ration back to 5.76:1 which was close to "standard", but I opted for a 18 tooth sprocket which pushed it up to 5.44:1. That effectively means that the engine is revving about 6% slower than standard gearing for any given road speed. My G3/LS pulls that gearing easily and is is still acceptably tractable in top.
Hi guys, been a few months now and had a couple more runs and finally today got it on the flat and topped it out at 58 mph (gps on phone) though this was 2 up but my daughter ways not much (unlike myself) so I’m thinking I need to go the way you did Pharisee as my sprockets are….
Engine 18
Clutch 42
Gear box 17
Rear sprocket 42
Would 1 more tooth on the gearbox sprocket make much difference as in mph?
Are you sure youve bought the right bike for what you want to do, Neil? I would have thought two-up at near enough 60mph on a nigh on 70 year old 350 was more than enough.
Greybeard wrote: ↑Wed Aug 03, 2022 6:20 pm
Are you sure youve bought the right bike for what you want to do, Neil? I would have thought two-up at near enough 60mph on a nigh on 70 year old 350 was more than enough.
Steve
Thanks Steve, you have probably just told me exactly what I wanted to hear as it’s a special and I’ve never ridden a standard G3ls I don’t know what to expect so if that seems about right I will probably leave well alone it’s just I’ve only started to do some vmcc runs and as there are lots on newer bikes I don’t want to be left behind
) was just wondering what sort of engine revs I should be getting at certain road speeds and best way to measure them? I only ask as some of you are aware it has a norton box so I'm wondering if it might be a bit low geared as it seems to pull up quite easily from quite low road speeds in 4th.
I would have thought two-up at near enough 60mph on a nigh on 70 year old 350 was more than enough.
it’s just I’ve only started to do some vmcc runs and as there are lots on newer bikes I don’t want to be left behind 
